The present invention relates to a switch which may be shifted between a "closed" state wherein it provides a very low resistance path for electric current and an "open" state wherein it provides a relatively high resistance current path.
One use for the switch of the present invention relates to superconductive magnet coils. Such coils are typically maintained at very low temperatures in baths of liquid helium in closed vessels, such as Dewar vessels. For certain applications, it is desirable to enable selective provision of a current path having very low resistance, such as 10.sup.-9 ohms, between two points within the Dewar vessel. Conventional switches are not capable of providing current paths having such low resistance.
Superconducting materials provide very low electrical resistance at very low temperatures. Typically, a superconductive material has a transition temperature between 10.degree. K. and 20.degree. K., above which temperature it is a normal conductor having relatively high resistance.
In the past, it has been proposed to employ superconductors as switches by varying their temperatures. However, such switches have typically included continuous stabilizing matrices of relatively low resistance, and have typically been incapable of providing high resistance current paths when in open position.